Voltage regulator



Dec. 18, 1956 R. R. LAW

VOLTAGE REGULATOR 3 Sheets-Sheet l Filed Oct. 22, 1954 iiulf Q INVENTOR.

Russell R. Law

By ATTORNEY Dec. 18, 1956 R. R. LAW

VOLTAGE REGULATOR 3 Sheets-Sheet 2 Filed Oct. 22. 1954 vFIG.4

INVENTOR.

' Russell R. Low

ATTORNEY Dec. 18, 1956 R. R. LAW

VOLTAGE REGULATOR Filed Oct. 22, 1954 3 Sheets-Sheet I5 INVENTOR.Russell R. Low

ATTORNEY United States Patent VOLTAGE REGULATOR Russell R. Law, Wenham,Mass., assignor to Columbia Broadcasting System, Inc., a corporation ofNew York, doing business under the name CBS-'Hytron, a Division ofColumbia Broadcasting System, Inc., Danvers, Mass.

Application October 22, 1954, Serial No. 463,846

7 Claims. (Cl. 313-208) This invention relates in general to electronictubes and in particular to voltage regulator tubes.

Glow-discharge type voltage regulator tubes are well known and widelyused in the electronics industry. Their operation depends upon thefundamental physical phenomena that under proper conditions a glowdischarge exhibits a substantially constant voltage drop over arelatively wide range of current. That is, the volt-amperecharacteristics of a gaseous discharge has a region where the current issubstantially independent of the voltage.

This useful characteristic of a glow discharge is well known. It isbelieved that the slope of the characteristic in this region dependsupon the positive-ion concentration in the neighborhood of the anode. Inany event, it is possible by well known structures and adjustments ofgas pressure to adjust this slope as desired. The voltage drop on theother hand, is largely determined by the cathodefall or voltage betweenthe plasma and the cathode.

In the voltage regulator tube, the voltage drop is a most importantcharacteristic. This voltage drop depends upon many factors includingthe kind of gas, the pressure of the gas, the impurities in the gas, andthe character of the cathode surface. The cathode surface depends notonly upon the material of the cathode and the impurities on its surface,but upon the surface changes brought about by the glow discharge itself.

This dependence of the cathode surface on the discharge itself may beexplained in part as follows: The discharge is maintained by positiveions from the plasma falling 'down the potential hill surrounding thecathode and releasing electrons. These electrons in turn are attractedup this same potential hill and accelerated to such a velocity that theyionize the residual gas, thereby restoring the positive ions initiallylost from the plasma. The voltage drop must adjust itself to such avalue that equilibrium is established. This equilibrium is:

Electrons Electrons Positive ions leaving bombarding cur rz ii a i oss Ithe cathode the cathode discharge However, the ratio of the number ofelectrons leaving the cathode to the number of positive ions bombardingthe cathode depends upon the surface condition, i. e., Work function,etc. This, in turn, is altered by positive ion bombardment. Therelatively massive positive ions strike the surface with suificientenergy to strip off the surface layers.

In tubes of conventional design the glow-discharge is not constrained toa particular path. After the arc is started, it may alter the cathodesurface in that particular zone to such an extent that the original pathis not the most favorable arc path. The arc will then jump to a new morefavorable path. Because of the differences in surface conditions, thisshift in arc path is ordinarily accompanied by a change in voltage. Thiserratic, unpredictable change in voltage is a major defect inconventional glow-discharge type voltage regulator tubes.

Therefore, it is an object of the present invention to provide voltageregulator tubes having a constant voltage drop throughout their life.

It is a further object of the present invention to provide a structurefor a voltage regulator tube which constrains the discharge to apredetermined path.

It is a still further object of the present invention to provide voltageregulator tubes having stable characteristics and long useful life.

In general, the present invention consists in a structure wherein thecathode and anode of a voltage regulator tube are so designed and spacedone from another that control of the discharge is maintained in apredetermined area. This is accomplished by locating the cathode of thetube in such relationship to the anode that a region of minimum spacingis provided. The configuration and orientation of the anode and thecathode are such that any movement of the arc to a path other than thatpredetermined is inhibited by an increase in arc length. For a betterunderstanding of the invention, together with other and further objects,features, and advantages, reference should be made to the followingdescription which is to be read in connection with the accompanyingdrawings in which:

Fig. 1 is an elevation view, partly cut away, of a voltage regulatortube incorporating the principles of the present invention;

Fig. 2 is a section taken through the tube of Fig. 1 along the line 2-2;

Fig. 3 is an elevation view, partly cut away, of another embodiment ofthe present invention in a voltage regulator tube;

Fig. 4 is a section taken through the tube of Fig. 3 along the line 44;and

Fig. 5 is a front elevation, partly cut away, of an operative voltageregulator tube embodying the principles of the present invention.

Referring particularly to Fig. 1, there is illustrated a tube which isof the miniature type, the glass envelope being removed for ease ofunderstanding. As is conventional in such tubes, the mount includes agetter 13 disposed upon the electrodes adjacent the top of the bulbwhere it is accessible for flashing to aid evacuation of the tube afterfinishing. A baflle mica 14 is provided beneath getter 13 to prevent thedeposition of getter material on working electrodes of the tube.

A cathode 15 is provided and has the shape of a cylinder. The actualactive surface of the cathode is the inner wall of the cylinder. Sincethe current handling capacity of tubes such as that of the presentinvention is determined in large part by the cathode area, normalelectrode structures are reversed, the cathode, as noted, being arelatively large cylindrical structure. An anode 16, is provided Withincylindrical cathode 15 and takes the shape of a rod. A disc 17 is placedwithin cathode 15 and is welded or otherwise maintained in good physicaland electrical contact therewith. A stem 18, of conventional design hassuitable leads sealed therethrough and connected to cathode 15 and anode16. These leads, of course, provide both support and electricalconnection to the electrode of the tube.

Referring now to Fig. 2, more detail on disc 17 is shown. Anode 16 andcathode 15 are concentrically disposed. The structure of disc 17 issuch, however, that an opening of circular shape is formed therein. Thisopening is not concentric with anode 16 or cathode 15 and, therefore, isdisposed relative to anode 16 such that an area of minimum spacing isprovided. In an actual embodiment of the present invention as built intoan operative regulator tube this spacing was .018".

Referring now to Fig. 3, a second embodiment incorporating the presentinvention is disclosed. In this figure, getter 13, baflle 14, cathode 15and anode 16 are all identical to those disclosed in Fig. 1. Also, thestem 18 with its leads is identical to that of Fig. 1. For convenience,the envelope has been removed in this view as well. However, the disc 27replaces the disc 17 shown in Fig. 1. Disc 27 has a cylindrical portionthereof which is welded to the inner surface of the cathode, cylinder 15and a conical section beneath the cylindrical section which tapers to anopening surrounding anode 16. As may be seen in Fig. 3 and also in Fig.4, the lower opening in conical section 27 is eccentric in respect toanode 16 and cylinder 15. In some instances, the conical shape of disc27 is preferred over that disclosed in Fig. 1 as a means to bettercontrol the region in which the arc strikes when the tube is being used.

In operation, it has been demonstrated that the arc prefers to strikeacross the region of minimum spacing because of the greater gradient inthat region. Moreover, the arc continues across that path with theresult that the objections of erratic, unpredictable voltage change asfound in conventional glow-discharge voltage regulator tubes areovercome. This situation obtains for the life of the tube, despite thefact that ion bombardment alters the cathode surface to some extent.Stable operating characteristics can be postulated with the structure ofthe invention and are not subject to objectionable change.

Referring now to Fig. 5, one embodiment of the present invention may beseen incorporated in an operative tube. In this figure, the electrodestructure is the same as that shown in Figs. 1 and 3. That is, the tube12 has a cylindrical cathode 1S and a rod-like anode 16 concentricallymounted therein, a getter 13, a baflie mica 14 and a stem 18 havingleads sealed therethrough. A disc 17 is shown sealed within the cathode15 although it should be noted that a conical section such as thesection 27 in Fig. 3 could be utilized in place of disc 17.

After assembly of the heretofore described parts in the envelope 10, theenvelope may be exhausted, filled with one of the numerous gases usefulin glow discharge tubes, such as argon, and then sealed. The pressure ofthe gas is predetermined to adjust the striking voltage of the tube asdesired. In addition, the inner surface of the cathode 15 may be coatedwith a rare earth metal such as cesium to change the characteristics ofthe tube 12. However the characteristics of the tube 12 are changed toprovide different operating ranges, it will be found that, if either theflat disc 17 or the conical section 27 is incorporated in the tube 12,much closer control of the characteristics is obtained without anyspecial precautions being taken as to the alignment of such a disc orconical section.

Although preferred embodiments have been shown and described, thisinvention should not be limted to the details disclosed. The concept ofestablishing and maintain ing an arc in a predetermined region isbelieved to be novel in its application to glow-discharge voltageregulator tubes, and the appended claims to structure embodying thisconcept are believed to define the invention comrnensurately.

What is claimed is:

1. In a glow-discharge voltage regulator tube, an anode, a cathodesurrounding said anode, and a circular insert connected to and withinsaid cathode, said insert having a portion thereof spaced more closelyto said anode than the remainder thereof.

2. A glow-discharge voltage regulator tube comprising, an envelopecontaining ionizable gas, a cylindrical cathode having a circularopening therethrough, a cylindrical anode disposed within said opening,the axes of said cylindrical cathode and said cylindrical anode beingcommon but displaced from the axis of said circular opening.

3. A glow-discharge voltage regulator tube comprising, an envelopecontaining ionizable gas, a cylindrical cathode having an openingtherethrough, a circular insert within and connected to said cathode,said insert having a substantially circular opening therethroughdisposed eccentrically of said cathode, and an anode concentric withsaid cathode passing through said opening.

4. A glow-discharge voltage regulator tube comprising, an envelopecontaining an ionizable gas, a cylindrical cathode having an axialopening therethrough, a circular insert within and connected to saidcathode, said insert having a substantially circular openingtherethrough disposed eccentrically of said cathode, and an anode ofsmaller outside diameter than the diameter of said opening in saidcircular insert, said anode being concentric with said cathode.

5. A glow-discharge voltage regulator tube comprising, an envelopecontaining ionizable gas, an anode disposed centrally of said envelope,a cathode concentric with and surrounding said anode, a substantiallyconical insert within and connected at its large end to said cathode,said conical insert having an eccentric opening in the small endthereof, said anode passing through said opening.

6. A glow discharge tube including an envelope containing an ionizablegas, a tubular electrode having a longitudinal axis, an insert connectedinternally of said tubular electrode and containing. an opening havingan axis parallel to the axis of said tubular electrode, and

a rod electrode having a longitudinal axis passing through said opening,at least one of said axes being displaced from another of said axes.

7. A glow discharge tube including an envelope containing an ionizablegas, a tubular electrode, an insert arranged transversely of saidtubular electrode and having an opening therein, and a rod electrodearranged within said tubular electrode and within said opening with asingle point on the edge of said opening nearer to said rod electrodethan any other point on said edge.

References Cited in the file of this patent UNITED STATES PATENTS1,760,524 Rentschler May 27, 1930 2,194,432 Pomfrett Mar. 19, 19402,401,911 Corson June 11, 1946

